Originally Posted by ntxsec

Last month I decided to tackle the high idle issue on my 89 560 SEC by removing the Idle Control Valve and cleaning it with carb cleaner and lubricated it with WD 40. When I removed it I inspected both elbow hoses and noticed one was cracked so I replaced it. After I got it back together I noticed the car was running rich (occasional smoke at idle more significant at startup).
I adjusted the fuel mixture a little leaner but it didn't help. I adjusted a few more times 1/4 turn each before I was at full lean. It still smelled real rich. I took it out for a highway run and noticed when I decellerated the engine speed seemed to surge between 2000 and 1500 rpm. When I got home and put it in park the idle speed jumped up to 1500 rpm. I got out of the car removed the electrical connection to the ICV and idle speed increased to 2000. So I replaced the connector and looked at every vacuum line under the hood, with no luck at finding other cracked vaccuum lines. I drove the car once more and the idle speed has increased to 2000 rpm. I'm stumped...whats causing this idle and unnecessary richness?

D